Add stats of client and pool to be accessible through agent

lib/core/symbols.js

@@ -64,5 +64,6 @@ module.exports = {
   kMaxConcurrentStreams: Symbol('max concurrent streams'),
   kNoProxyAgent: Symbol('no proxy agent'),
   kHttpProxyAgent: Symbol('http proxy agent'),
-  kHttpsProxyAgent: Symbol('https proxy agent')
+  kHttpsProxyAgent: Symbol('https proxy agent'),
+  kStats: Symbol('stats')
 }

lib/dispatcher/agent.js

@@ -1,7 +1,7 @@
 'use strict'
 
 const { InvalidArgumentError } = require('../core/errors')
-const { kClients, kRunning, kClose, kDestroy, kDispatch } = require('../core/symbols')
+const { kClients, kRunning, kClose, kDestroy, kDispatch, kUrl } = require('../core/symbols')
 const DispatcherBase = require('./dispatcher-base')
 const Pool = require('./pool')
 const Client = require('./client')
@@ -110,6 +110,17 @@ class Agent extends DispatcherBase {
 
     await Promise.all(destroyPromises)
   }
+
+  get stats () {
+    const stats = []
+    for (const client of this[kClients].values()) {
+      const stats = client.stats
+      if (stats) {
+        stats.push([client[kUrl], stats])
+      }
+    }
+    return stats
+  }
 }
 
 module.exports = Agent

lib/dispatcher/client-stats.js

@@ -0,0 +1,28 @@
+'use strict'
+
+const { kConnected, kPending, kRunning, kSize } = require('../core/symbols')
+const kClient = Symbol('client')
+
+class ClientStats {
+  constructor (client) {
+    this[kClient] = client
+  }
+
+  get connected () {
+    return this[kClient][kConnected]
+  }
+
+  get pending () {
+    return this[kClient][kPending]
+  }
+
+  get running () {
+    return this[kClient][kRunning]
+  }
+
+  get size () {
+    return this[kClient][kSize]
+  }
+}
+
+module.exports = ClientStats

lib/dispatcher/client.js

@@ -7,6 +7,7 @@ const util = require('../core/util.js')
 const { channels } = require('../core/diagnostics.js')
 const Request = require('../core/request.js')
 const DispatcherBase = require('./dispatcher-base')
+const ClientStats = require('./client-stats')
 const {
   InvalidArgumentError,
   InformationalError,
@@ -51,7 +52,8 @@ const {
   kOnError,
   kHTTPContext,
   kMaxConcurrentStreams,
-  kResume
+  kResume,
+  kStats
 } = require('../core/symbols.js')
 const connectH1 = require('./client-h1.js')
 const connectH2 = require('./client-h2.js')
@@ -249,6 +251,8 @@ class Client extends DispatcherBase {
 
     this[kResume] = (sync) => resume(this, sync)
     this[kOnError] = (err) => onError(this, err)
+
+    this[kStats] = new ClientStats(this)
   }
 
   get pipelining () {

lib/dispatcher/pool-base.js

@@ -2,7 +2,7 @@
 
 const DispatcherBase = require('./dispatcher-base')
 const FixedQueue = require('./fixed-queue')
-const { kConnected, kSize, kRunning, kPending, kQueued, kBusy, kFree, kUrl, kClose, kDestroy, kDispatch } = require('../core/symbols')
+const { kConnected, kSize, kRunning, kPending, kQueued, kBusy, kFree, kUrl, kClose, kDestroy, kDispatch, kStats } = require('../core/symbols')
 const PoolStats = require('./pool-stats')
 
 const kClients = Symbol('clients')
@@ -16,7 +16,6 @@ const kOnConnectionError = Symbol('onConnectionError')
 const kGetDispatcher = Symbol('get dispatcher')
 const kAddClient = Symbol('add client')
 const kRemoveClient = Symbol('remove client')
-const kStats = Symbol('stats')
 
 class PoolBase extends DispatcherBase {
   constructor () {